Let’s start with some grounding facts: Frogs are part of the Anura order of amphibians. Anura means without a tail. So, what about toads? Yes, it includes them too. Technically speaking, all toads are frogs, but not all frogs are toads.
This is relevant because they share some of their winter survival habits which we will see as we discuss the various overwintering tactics.
There are different approaches to winter depending on the type of frog. Aquatic frogs such as the American Bullfrog (Rana catesbeiana) and the Northern Leopard Frog (Rana pipiens) live in and around rivers and ponds. Therefore, it’s probably not surprising that they hibernate in the water. However, unlike turtles who need little oxygen in this state, frogs need oxygen. When winter approaches, they will sink to a deeper, oxygen-rich depth of the water then they will slow their metabolism down and wait out the season.
Other species that live on land such as our locally ubiquitous Spring Peepers (Hyla crucifer) and Wood Frogs (Rana sylvatica) hibernate in leaf litter and other crevices. They increase their concentration of glucose and sugar alcohols to preserve their organs much like antifreeze does in your car engine. As a result, these frogs can freeze and still survive. Ice crystals can be found in their bodies. When warmer temperatures arrive, they will thaw out and the organs begin to function again.
The American Toad (Bufo americanus), a land dweller and the only type of toad found in Maine, digs down in the soil to get below the frost line. The Fowler’s Toad (Anaxyrus fowleri), found in the Midwest, Mid-Atlantic, and other parts of New England, also borrows down. In contrast, the Great Plains Toad (Anaxyrus cognatus), found in the plains states and up into Canada, may use dormant rodent burrows for its winter domicile.
Of course, not all frogs need a winter survival strategy. Many types live in areas where the temperature rarely dips below 32°.
Lastly, the frogs’ adaptation strategies are not foolproof. Some can resist lower temperatures than others, so our increasingly erratic shifts in weather and climate make it difficult for them to survive.
This is a problem. Did you know that frogs are an indicator species? What this means is that they provide an early indication of the declining health of an environment. Because of their permeable skin, they are highly sensitive to changes in pollution, bacteria, algae, UV, and pH levels. The news isn’t good, most frog species have been on a severe decline for the past several decades.
Without the frogs, we will invariably have more mosquitoes and other pesky bugs. Plus, they are a major component of the food chain for birds, fish, snakes, and some mammals. Let’s work towards a better outcome for our frog friends, and ultimately for ourselves.
Frogs in winter — https://www.scientificamerican.com/article/how-do-frogs-survive-wint/
More about the Great Plain’s Toad — http://fieldguide.mt.gov/speciesDetail.aspx?elcode=AAABB01050